A mobile device typically includes an RF power amplifier that amplifies an RF signal during transmission and reception of the RF signal. RF power amplifiers may include a pre-driver stage, a main stage, a bias circuit for driving amplifier circuits of the pre-driver stage and the main stage, an inter-stage impedance matching network between the pre-driver stage and the main stage, an output impedance matching network at an output terminal, and a control circuit for controlling the operation of the RF power amplifier. In particular, the control circuit may control the amplifier circuits of the pre-driver stage and the main stage.
Conventionally, RF power amplifiers may be either complementary metal-oxide semiconductor (CMOS) power amplifiers formed by CMOS integrated circuits (ICs) having CMOS transistors, or HBT power amplifiers formed by ICs having HBTs. HBTs typically operate with good linearity and high efficiency, so that HBT power amplifiers consequently may provide good RF performance with high reliability. HBT power amplifiers therefore have been widely utilized in the mobile power amplifier industry. However, ICs having HBT power amplifiers suffer from a number of drawbacks including high wafer cost and complicated IC manufacturing processes due to the complicated configuration of ICs.
In contrast, CMOS power amplifiers formed by ICs having the CMOS transistors typically have low manufacturing cost, but may however have performance shortcomings due to power loss and/or the non-linear characteristics of CMOS transistors. In addition, when CMOS power amplifiers are used for amplification of an RF signal having a wide frequency band, signal distortions may occur due to the high parasitic input capacitance of CMOS transistors, particularly in the case of P-channel metal oxide semiconductor (PMOS) transistors.